The present invention generally relates to a piezoelectric vibrator and, more particularly, to a piezoelectric vibrator of a type employing a combination of a mechanical vibrator and a piezoelectric transducer.
An example of prior art piezoelectric tuning forks is shown in FIG. 1 of the accompanying drawing, and comprises a fork vibrator 11 made of elastic invariable metal, such as elinvar, and having a pair of prongs 12 connected integrally together by a bridge portion 13 to assume a generally U-shaped configuration, and a piezoelectric transducer 16 which is formed by a piezoelectric layer 14 made of a piezoelectric material such as, for example, ZnO, in the form of a piezoelectric thin film and applied over the entire outer surface of one of the prongs 12 facing in a direction opposite to the other of the prongs 12, and an electrode layer 15 made of, for example, Au or Al, and overlaying the piezoelectric layer 14. The assembly is mounted, on a generally cylindrical stem member 17 made of an electrically insulating material and having terminal pins 18 and 19 extending axially completely through the stem member 17 and also having a support pin 20 extending axially from the stem member 17 towards the assembly, respective ends of the pins 18 ad 20 adjacent the assembly being secured to one of the opposite, generally U-shaped surface of the fork vibrator 11 while the electrode layer 15 is connected to the pin 19 through a wire 21 by the use of a wire bonding technique.
The prior art piezoelectric tuning fork shown in and described with reference to FIG. 1 has such a disadvantage in that, since the piezoelectric layer 14 is deposited direct on a surface area of the fork vibrator 11, the resonance frequency relative to temperature tends to vary considerably.
In view of the above, an attempt has been made to use a capacitor to compensate for variation of the resonance frequency relative to temperature, but this attempt has been found unsatisfactory. This disadvnatage is generally inherent in a piezoelectric tuning fork comprising a combination of a vibrating fork and a piezoelectric transducer, a piezoelectric vibrator comprising a mechanical vibrating element and a piezoelectric transducer and the like.